Micromechanical Origin of Particle Size Segregation

Jing, Lü; Kwok, C. Y.; Leung, Yiu-Wing

doi:10.1103/physrevlett.118.118001

Cited by 83 publications

(76 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To explain the stratification phenomenon in

v_{k}^{h}

distributions of different sized particles, the squeeze expulsion theory, which was proposed by Savage and Lun (), is employed in this study. The squeeze expulsion theory assumes that force imbalances can be developed such that particles are squeezed out of their own positions into other positions to form stratification phenomenon in granular flows (Jing et al, ; Zhou & Ng, ; Zhou, Lai, et al, ). Based on the squeeze expulsion theory, a parameter

T_{k}^{h}

is then defined to quantify the mechanical imbalance effects on different sized particles caused by particle interactions:

T_{k}^{h} = \frac{1}{N_{k}} \sum_{i = 1}^{N_{k}} \frac{|F_{i}^{h}|}{italicρπ r^{2} n} ((),,, k = normals, m, l)

…”

Section: Resultsmentioning

confidence: 99%

Collapse of Granular Columns With Fractal Particle Size Distribution: Implications for Understanding the Role of Small Particles in Granular Flows

Liu

Vallejo

Zhou

et al. 2017

Geophysical Research Letters

View full text Add to dashboard Cite

According to field measurements, the basic character of the particle size distributions obtained from the landslide accumulations is fractal. The collapse of the granular columns with fractal particle size distribution (FPSD) is performed numerically and experimentally to form dry granular flows and the mechanism of how FPSD affects the particle movements is then investigated. Numerical and experimental analyses show that particle flow mobility increases as the fractal dimension increases. Several linear relationships exist between the fractal dimension and flow mobility parameters. By analyzing the kinetics of granular flows, it is found that a large number of small-sized particles will form a boundary layer where the particle shearing and velocities are remarkably increased and will thus have a lubricant effect on the flow mobility. Moreover, the number of particle collisions increases, and small-sized particles are more likely to obtain higher spreading velocities via the greater contribution of particle interactions.

show abstract

“…To explain the stratification phenomenon in

v_{k}^{h}

T_{k}^{h}

is then defined to quantify the mechanical imbalance effects on different sized particles caused by particle interactions:

T_{k}^{h} = \frac{1}{N_{k}} \sum_{i = 1}^{N_{k}} \frac{|F_{i}^{h}|}{italicρπ r^{2} n} ((),,, k = normals, m, l)

…”

Section: Resultsmentioning

confidence: 99%

Collapse of Granular Columns With Fractal Particle Size Distribution: Implications for Understanding the Role of Small Particles in Granular Flows

Liu

Vallejo

Zhou

et al. 2017

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…That is, at steady-state the magnitude of the directed rearrangement mechanism of segregation balances the random collisional diffusion mechanism that remixes particles. Furthermore, when the system becomes highly segregated, large or light particles can sometimes become trapped in regions with many small or heavy particles, which limits the ultimate degree of segregation [13,[25][26][27][28].…”

Section: A Quantifying Segregationmentioning

confidence: 99%

Effect of pressure on segregation in granular shear flows

et al. 2018

View full text Add to dashboard Cite

The effect of confining pressure (overburden) on segregation of granular material is studied in discrete element method (DEM) simulations of horizontal planar shear flow. To mitigate changes to the shear rate due to the changing overburden, a linear with depth variation in the streamwise velocity component is imposed using a simple feedback scheme. Under these conditions, both the rate of segregation and the ultimate degree of segregation in size bidisperse and density bidisperse granular flows decrease with increasing overburden pressure and scale with the overburden pressure normalized by the lithostatic pressure of the particle bed. At overburdens greater than approximately 20 times the lithostatic pressure at the bottom of the bed, the density segregation rate is zero while the size segregation rate is small but nonzero, suggesting that different physical mechanisms drive the two types of segregation. The segregation rate scales close to linearly with the inertial number for both size bidisperse and density bidisperse mixtures under various flow conditions, leading to a proposed pressure dependence term for existing segregation velocity correlations. Surprisingly, particle stiffness has only a minor effect on segregation, although it significantly affects the packing density.

show abstract

“…The number of particles of each species is thus simply given by N p /N s , where N p is the total number of particles. We consider regular polygonal particles with the number of sides n s ∈ [3,4,5,6,7,8,10,15,20], and circular particles. So, α i which will refer as the angularity of the specie i is simply given by 2π/n i s , where n i s is the number of side of the specie i.…”

Section: Numerical Procedures Packing Construction and Biaxial mentioning

confidence: 99%

“…Samples containing different particles sizes (polydisperse) have been extensively analyzed [6,[14][15][16][17][18][19][20], showing some counterintuitive results such as the independence of the macroscopic friction with respect to the grain size span [21,22], the shape of the GSD [23,24], and stiffness and Poisson's ratio of the particles [25,26].…”

Section: Introductionmentioning

confidence: 99%

Effects of particle shape mixture on strength and structure of sheared granular materials

2019

View full text Add to dashboard Cite

To cite this version:Theechalit Binaree, Itthichai Preechawuttipong, Emilien Azéma. Effects of particle shape mixture on strength and structure of sheared granular materials.Using bi-dimensional discrete element simulations, the shear strength and microstructure of granular mixtures composed of particles of different shapes are systematically analyzed as a function of the proportion of grains of a given number of sides and the combination of different shapes (species) in one sample. We varied the angularity of the particles by varying the number of sides of the polygons from 3 (triangles) up to 20 (icosagons) and disks. The samples analyzed were built keeping in mind the following cases: (1) increase of angularity and species starting from disks; (2) decrease of angularity and increase of species starting from triangles;(3) random angularity and increase of species starting from disks and from polygons. The results show that the shear strength vary monotonically with increasing numbers of species (it may increase or decrease), even in the random mixtures (case 3). At the micro-scale, the variation in shear strength as a function of the number of species is due to different mechanisms depending on the cases analyzed. It may result from the increase of both the geometrical and force anisotropies, from only a decrease of frictional anisotropy, or from compensation mechanisms involving geometrical and force anisotropies.

show abstract

Micromechanical Origin of Particle Size Segregation

Cited by 83 publications

References 46 publications

Collapse of Granular Columns With Fractal Particle Size Distribution: Implications for Understanding the Role of Small Particles in Granular Flows

Collapse of Granular Columns With Fractal Particle Size Distribution: Implications for Understanding the Role of Small Particles in Granular Flows

Effect of pressure on segregation in granular shear flows

Effects of particle shape mixture on strength and structure of sheared granular materials

Contact Info

Product

Resources

About